Helicobacter pylori infections in humans are a major cause of gastric and duodenal ulceration as well as gastric cancer. H. pylori is not the only Helicobacter species capable of colonizing the human gastric mucosa. “Helicobacter heilmannii” (proposed name) has been found in approximately 0.96% of gastric biopsies in humans (Heilmann & Borchard (1991) Gut 32, 137-140). This organism is strongly associated with gastritis but is also associated with peptic ulceration, gastric adenocarcinoma, and mucosa-associated lymphoid tissue lymphoma. Recent evidence indicates that “H. heilmannii” is not a single species but represents different bacterial species with similar spiral morphologies, most of which are probably of zoonotic origin. Classification into “H. heilmannii” type 1 and “H. heilmannii” type 2 was established on the basis of 16S rRNA gene sequences (Solnick et al., (1993) J. Infect. Dis. 168, 379-385). More than 50% of the “H. heilmannii” infections in humans are due to “H. heilmannii” type 1 (Trebesius et al. (2001) J. Clin. Microbiol. 39, 1510-1516.). “H. heilmannii” type 1 has been shown to be identical to “Candidatus H. suis” (O'Rourke et al. (2004) Int. J. Syst. Evol. Microbiol. 54, 2203-2211), a hitherto non-culturable spiral bacterium that colonizes the stomachs of more than 60% of slaughter pigs. The actual role of Candidatus H. suis in gastric disease in pigs is still a matter of debate, but it has been suggested that this bacterium is associated with gastric ulceration of the pars oesophagea and with chronic pyloric gastritis. Mouse inoculation was used to isolate this bacterium from infected pig stomach mucosa (Dick et al., (1989) J. Med. Microbiol. 29, 55-62). Hellemans et al. ((2005) Antimicrob. Agents Chemother. 49, 4530-4535) modified the existing in vivo mouse model of Candidatus H. suis infection, for evaluating the antibiotic susceptibility of this organism. In vitro cultivation of Candidatus H. suis has not been achieved yet.